Type 1 diabetes is a devastating chronic illness that develops when multiple genetic factors combined with undetermined environmental events lead to self recognition and destruction of pancreatic beta cells. The death of beta cells is mediated by cytotoxic T lymphocytes (CTL) that recognize peptide epitopes on the surface of beta cells in the context of HLA class I molecules. Using interferon-gamma ELISpot assays and HLA-A201 tetramers, we have identified two peptide epitopes that are recognized by a population of CTL in patients with recent onset diabetes. We believe that this methodology may be expanded and exploited to identify further beta cell epitopes. By combining the resources of B.C.'s Children's Hospital with those of the Barbara Davis Center for Childhood Diabetes, we propose to screen groups of pre-diabetic and diabetic patients in order to identify novel HLA class I restricted beta cell epitopes. In addition, we believe that analogs of these epitopes may be useful both in predictive and preventive technologies for disease and therefore, we intend to screen heteroclitic peptides in order to identify optimal ligands with higher binding affinities. Finally, we will determine the utility of both Elispots and tetramers for the detection of beta cell specific CTL in pre-diabetic subjects. These approaches will allow us to develop and optimize both ELISPOT and tetramer assays for predicting disease in humans and lay the groundwork for peptide tolerizing vaccines. The work proposed has significant potential to lead to novel, sensitive and specific assays for predicting diabetes in humans, as well as to the development of peptide vaccines for preventing or delaying the onset of this common human disease.